Longitudinal Associations Between Use of Tobacco and Cannabis Among People Who Smoke Cigarettes in Real-world Smoking Cessation Treatment.

Objectives: Cannabis use is common among people who use tobacco. However, little is known about the relationship between change in use of tobacco and cannabis over time. We examined the longitudinal associations between use of the two substances in a realworld smoking cessation context.

Methods: This study analyzed data from a 3-month smoking cessation program delivered via Facebook in the San Francisco Bay Area, USA during 2016-2020. The sample included 487 participants who smoked cigarettes ( Mage = 25.4 years old, 39.6% Male, 40.3% White). The regressors (ie, frequency or number of days during the past 30 days using cigarettes, e-cigarettes, and cigars) and the outcome (ie, frequency of cannabis use) were measured at both baseline and 3-month follow-up. Random-effects modeling examined the longitudinal associations between the regressors and the outcome controlling for alcohol use and baseline demographics.

Results: Participants who increased (or decreased) their frequency of use of cigarettes (β = 0.17, 95% confidence interval [CI] = 0.10, 0.24), e-cigarettes (β = 0.11, 95% CI = 0.05, 0.17), or cigars (β = 0.19, 95% CI = 0.06, 0.32) also increased (or decreased) their frequency of cannabis use after 3 months. Sexual minority participants (vs heterosexuals) (β = 2.12, 95% CI = 0.01, 4.24) and those whose education attainment being high school or less (vs higher education) (β = 3.89, 95% CI = 1.25, 6.53) were more likely to increase their frequency of cannabis use over time.

Conclusions: The findings indicated positive associations between change in use of tobacco and cannabis use. Promoting cessation among people who use tobacco may help to reduce their cannabis use.